The present invention is directed toward metallizing the surface area, or portions thereof, of a non-conductive substrate with a suitable and desirable finish layer of metal. For example, it has long been considered desirable to provide ceramic tiles and the like, for use in bathroom or pool area flooring and walls where durability and water imperviousness are primary considerations. Such tiles have long been provided with colorants, or have been painted with metallic paints and "fired" in order to have different colors and designs thereon for aesthetic reasons.
The type of metallic finish articles which have heretofore been known in the art, have had the drawback of not being capable of retaining a high polish or shine. Further, articles that have metallic paint applied often prove to be incapable of withstanding exposure to conditions normally encountered in their intended environment. The metallic finish frequently wears off or dulls in a short time period relative to the normal service life of the tile, leaving no choice but to replace the entirety of the article, usually at great expense.
Conventional electroplating has been a known technology for many years, and is considered useful for providing a durable finish to a conductive article. Because of the requirement that the plated surface be conductive, conventional electroplating processes have not heretofore been useful for metallizing non-conductive substrates.
The metallizing of non-conductive substrates has been limited commercially to only certain materials or to what are essentially experimental laboratory procedures. For instance, processes are known for treating plastics such as acrylonitrile-butadiene-styrene copolymer (ABS). These processes have employed acid etches such as may be accomplished in a chromic sulfuric bath. These processes are not useful for preparing non-conductive substrates such as ceramic, glass or porcelain. The metallizing methods heretofore known in the art for polymeric materials are not capable of metallizing these later types of substrates except by using solutions having a very high acid concentration. These high acid concentrations are known to be very hazardous to both the operators of the involved processes and to the articles themselves.
A need exists, therefore, for a durable, metallized product having a non-conductive substrate of ceramic, glass, porcelain, clay or other such material. Further, a need exists for a process for producing such a metallized article without the danger to operators and the articles that are associated with processes employing solutions having high acid concentrations.